An aggressive strain of mice has a higher steady-state concentration as well as turnover of catecholamine in the frontal cortex, caudate nucleus and hypothalamus when compared to a docile strain, suggesting that neuronal activity in these areas may be greater in aggressive mice. Norepinephrine and dopamine levels and turnover were measured in 17 discrete brain regions of Swiss-Webster (NIH) controls. The norepinephrine steady-state level was significantly lower in olfactory tubercle and substantia nigra and significantly higher in the septal area of the aggressive mice. Norepinephrine turnover was only higher in the A-10 region (ventral tegmental area) of the aggressors. Dopamine steady-state level and turnover was lower in olfactory tubercle and higher in caudate putamen of the aggressors.